Micromechanical study of stress distribution in unidirectional composites with polymeric resin affected by crack

The history of the use of fiber reinforced composites goes back to the last decade, with the use of these materials in various industries such as aerospace, automotive, construction and so on.

Much research has been done on the behavior of micro-scale composites. One of the most thorough reviews and data gathering has been done by Jones. Micro-mechanics and macro-mechanics are a good segmentation to study the behavior of composites

. In other words, micromechanics is the analysis of composite behavior in interaction with constituent materials, while macromechanics is the analysis of composite behavior at the structural scale. The properties of a layer can be determined using the test results in the built state or can be estimated mathematically based on the properties of the constituent materials. In other words, the properties of the layer can be predicted by micromechanical methods or the properties of the layer can be measured by physical and macro-mechanical means. Micromechanics When macromechanics is preferred, material properties are preferred to structural properties in analysis. By careful design, it can be shown that the micromechanical predictions of the properties of a layer based on the properties of the constituents correspond to the measured properties. Micromechanical analysis has limitations that need to be verified by rigorous testing.

Band [2] and his colleagues conducted experiments on fibers with rectangular and circular cross-sections, and the results showed that fibers with circular cross-sections had 20% higher tensile strength than composites. They are circular fibers. Micro-mechanical tests have also shown that composites consisting of rectangular cross-sections are 60% more durable. Tensile and compressive mechanical tests have also been performed on glass fiber reinforced plastic materials with rectangular and circular cross-sections. The results show that in the tensile and compressive conditions of the rectangular fibers, they are 20% and 40% more robust, respectively. Shear tests have shown that the rectangular section has a 5% strength.

Attar and Rabati studied stress concentration values ​​near pin holes in multilayer composites made of glass fibers with rectangular, circular and hexagonal cross sections. In these papers, the effect of geometrical parameters such as gap-to-edge-to-diameter ratio, sheet-to-diameter ratio, and gap-to-diameter ratio on stress distribution in a unidirectional composite sheet with two pin-induced gaps The analytical and numerical form is examined. In these studies, it is assumed that all fibers are in the same direction, while loading is defined as P once infinite. Differential equations based on shear crank models are defined for a model with different geometries. The results of the analytical methods are also compared with the 3D finite element method and very close responses are observed. Finally, the effect of different pin diameters on shear stress distribution in layered composites is investigated.

Joshi et al. [3] investigated the effects of the carbon nanotube orientation on the elastic properties of the nanocomposite without considering the middle phase effects. In this micromechanical discussion, the distribution of carbon nanotubes in the field was modeled on a regular basis. Boxer and Robinson [5] investigated the effects of the middle phase modulus on the elastic properties of nanocomposites with regular distribution of nanoparticles by micromechanical modeling. Joshi and Eupadia [6] studied the effects of the middle phase on the elastic properties of nanocomposites consisting of multi-walled nanotubes with finite element micro-mechanical distribution. Jasmine and Heshmati use the Mori-Tanaka micromechanical model to obtain the elastic properties of carbon nanotube-reinforced polymer to analyze the dynamic behavior of nanocomposites.

[1] Jones

[2] Bond

[3] Joshi

[4] Baxter

[5] Robinson

[6] Upadhyay

In micromechanical models due to the complexities of modeling, some of the assumptions are generally common, the assumptions used in this study being:

1. Fiber and matrix are considered isotropic separately

2. Considering the perfect connection between the fibers and the resin

Hardening behavior is considered cinematic.

8. Purpose of the research (including scientific, practical and specific purposes of the research)

The intrinsic goal of micromechanical investigations is to optimize the design and enhance the properties of the composites, which requires a thorough understanding of the deformation and fracture behavior of the composites. Different geometries of the surface of the fibers should also be examined to determine the effect of each geometry on the mechanical properties of the composite. Finally, by introducing the mechanical properties of each geometry, it is possible to select the ideal fibers according to the working conditions and mechanical properties required.